Method and apparatus for WLAN location services

ABSTRACT

Methods, apparatuses and systems directed to providing location services in a wireless network. According to one implementation of the present invention, the wireless network infrastructure provides high-accuracy location information via location services to wireless clients. In one embodiment, during an advertisement phase, a location server provides a list of available location services to wireless clients via a central controller. In another embodiment, during a presentation phase, a driver of the wireless client presents the available location services to one or more applications of the wireless client. In another embodiment, during a request phase, the driver transmits a location service request to the central controller, which passes the location service request to the location server.

FIELD OF THE INVENTION

The present invention relates to wireless networks and, moreparticularly, to methods, apparatuses, and systems directed to providinglocation services in a wireless network.

BACKGROUND OF THE INVENTION

Market adoption of wireless LAN (WLAN) technology has exploded, as usersfrom a wide range of backgrounds and vertical industries have broughtthis technology into their homes, offices, and increasingly into thepublic air space. This inflection point has highlighted not only thelimitations of earlier-generation systems, but also the changing rolethat WLAN technology now plays in people's work and lifestyles, acrossthe globe. Indeed, WLANs are rapidly changing from convenience networksto business-critical networks. Increasingly users are depending on WLANsto improve the timeliness and productivity of their communications andapplications, and in doing so, require greater visibility, security,management and performance from their network.

For some applications, it is desirable to provide location informationto the wireless clients. Some wireless infrastructures may provide theMAC address of a wireless access point or a basic service setidentification (BSSID), as a coarse-grained proxy for the actuallocation, to the client during an initial association between thewireless access point and the wireless client. However, such systems donot provide location information about the wireless client. The IEEE802.11k standard defines a mechanism for a wireless client to requestits location from the wireless infrastructure. This location isgenerally defined in location configuration information (LCI) (e.g.,latitude/longitude). The IEEE 802.11k standard does not support,however, location based services that support more than one locationservice type.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a topological diagram of the components in a wireless localarea network (WLAN) system according to one implementation of thepresent invention.

FIG. 1B illustrates a hierarchical wireless network including a centralcontroller, according to one implementation of the present invention.

FIG. 1C illustrates for didactic purposes a hardware system, which maybe used to implement a central controller.

FIG. 2 illustrates for didactic purposes a hardware system, which may beused to implement a wireless access point.

FIG. 3 illustrates for didactic purposes a hardware system, which may beused to implement a wireless client.

FIG. 4 is a diagram illustrating a possible message flow in accordancewith one implementation of the present invention.

FIG. 5 is a diagram illustrating a possible message flow in accordancewith one implementation of the present invention.

FIG. 6 is a flow chart illustrating a process flow, according to oneimplementation of the present invention, implemented at a wirelessclient.

FIG. 7 is a data structure of an exemplary location service IE accordingto one implementation.

FIG. 8 is a flow chart illustrating a process flow, according to oneimplementation of the present invention, implemented at a centralcontroller.

FIG. 9 is a flow chart illustrating a process flow, according to oneimplementation of the present invention, implemented at a locationserver.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A. Overview

The present invention provides methods, apparatuses, and systemsdirected to providing location services in a wireless network. Accordingto one implementation of the present invention, the wireless networkinfrastructure provides high-accuracy location information via locationservices to wireless clients, which may include any wireless devicecapable of receiving the location information (e.g., laptops, personaldigital assistants (PDAs), radio frequency identification (RFID) tags,etc.). For example, a location service may provide location informationthat describes where a particular wireless client is located in aparticular region (e.g., one square meter in accuracy) within aparticular city, campus, or building. As described in more detail below,in one implementation, location services may be categorized intolocation service classes. In one implementation, one location serviceclass may include on-demand location services, and another locationservice class may include update location services. In oneimplementation, for each location service class, the location server mayprovide to a wireless client a comprehensive set of location serviceoptions. For example, for update location services, update options mayinclude receiving update services based on one or more triggers, whichmay be based on events including time intervals, movement, containment,etc.

In one implementation, during an advertisement phase, a location serverprovides a list of its available supported location services to wirelessclients via one or more elements of the wireless network infrastructure.The location server provides to the wireless network infrastructure alist of available location services that the location server supports.The wireless network infrastructure may then advertise the availablelocation services to wireless clients. In one implementation, during apresentation phase, a wireless network interface driver of the wirelessclient presents the available location services to one or moreapplications of the wireless client. During a request phase, thewireless client transmits a location service request to the wirelessnetwork infrastructure, which passes the location service request to thelocation server. The location service request, in one implementation,may be a request to subscribe to an update location service or anon-demand request for one or more location services.

B. Exemplary Wireless Network System Architecture

B.1. Network Topology

A network environment including a wireless local area network (WLAN)according to one implementation of the present invention is shown inFIG. 1A. In a specific embodiment of the present invention, the systemincludes a location server 20, an Authentication Authorization andAccount (AAA) server 22, and a central controller 42, a local areanetwork (LAN) 30, a router 32, and wireless access points 50 a, 50 b, 50c, and 50 d (collectively referred to as wireless access points 50). LAN30 is implemented by a switch (or an array of switches) and/or othernetwork devices, such as a bridge. The location server supports avariety of location service categories and options, described below.

As FIG. 1A illustrates, these network elements are operably connected toa network 52. Network 52, in one implementation, generally refers to acomputer network, such as a LAN, a WAN, etc., that includes one or moreintermediate network devices (e.g., routers, switches, etc.), whichallow for the transmission of messages between location server 20, AAAserver 22, central controller 42, and wireless clients via wirelessaccess points 50. Of course, network 52 can include a variety of networksegments, transmission technologies and components, such as terrestrialWAN links, satellite links, optical fiber links, and cellular links;network 52 could also be a campus LAN. LAN 30 may be a LAN or LANsegments implemented by an Ethernet switch (not shown) or an array ofswitches having multiple ports to which wireless access points 50 areconnected. The wireless access points 50 are typically connected toswitch ports via Ethernet links; however, other link layer connectionprotocols or communication means can be employed. FIG. 1A illustratesone possible network environment in which the invention may operate;however, other implementations are possible. For example, although WLANmanagement server 20 is illustrated as being on a different LAN or LANsegment, it may be co-located with wireless access points 50.

The wireless access points 50 are operative to wirelessly communicatewith remote wireless client devices 60 a, 60 b, 60 c, and 60d. In oneimplementation, the wireless access points 50 implement the wirelessnetwork protocol specified in the IEEE 802.11 WLAN specification. Thewireless access points 50 may be autonomous or so-called “fat” wirelessaccess points, or light-weight wireless access points operating inconnection with a wireless switch (see FIG. 1B). In addition, thenetwork infrastructure may also include a Wireless LAN Solution Engine(WLSE) offered by Cisco Systems, Inc. of San Jose, Calif. or anotherwireless network management system. In some implementations, the networkinfrastructure may also include one or more Wireless Control System(WCS) nodes operative to manage one or more wireless switches and accesspoints.

B.2. Central Controller

FIG. 1B illustrates a hierarchical wireless network including a centralcontroller 70, which may be used to implement a central controller 42 ofFIG. 1B. In one implementation, central controller 70 may be used toadvertise available location services wireless clients and to receivelocation service requests from wireless clients according to oneimplementation of the present invention. In one implementation, thecentral controller 70 may be implemented as a wireless domain server(WDS) or, alternatively, as a wireless switch. If the central controller70 is implemented with a WDS, the central controller 70 is operative tocommunicate with autonomous or so-called “fat” wireless access points.If the central controller 70 is implemented as a wireless switch, thecentral controller 70 is operative to communicate with light-weightwireless access points and process wireless protocol and networkmanagement information.

FIG. 1C illustrates for didactic purposes a hardware system 100, whichmay be used to implement a central controller 70 of FIG. 1B. As FIG. 1Cshows, in one implementation, the central control elements each comprisea switch function or fabric 102 comprising a network interface 104 a(e.g., a Ethernet adapter) for connection to network 52 andcorresponding network interfaces 104 b, 104 c, and 104 d for connectionto the access elements, a processor 106, a memory 108, one or moresoftware modules, stored in memory 108, including instructions forperforming the functions described herein, and a system bus 110 operablyconnecting these components. The central control elements may optionallyinclude an administrative network interface 112 allowing foradministrative access for such purposes as configuration and diagnosticaccess. In other implementations, central controller includes a singlenetwork interface.

B.3. Wireless Access Point

FIG. 2 illustrates for didactic purposes a hardware system 300, whichmay be used to implement a wireless access point 50 of FIG. 1. In oneimplementation, the wireless access point 300 comprises a processor 310,a memory 312, a network interface 314 (e.g., an 802.3 interface) forcommunication with a LAN, a cache 316 for storing WLAN information, apersistent memory 318, a wireless network interface 320 (e.g., an IEEE802.11 WLAN interface) for wireless communication with one or morewireless clients 60, and a system bus 322 interconnecting thesecomponents. The wireless access points 50 may also include softwaremodules (including Dynamic Host Configuration Protocol (DHCP) clients,transparent bridging, Lightweight Access Point Protocol (LWAPP), Cisco®Discovery Protocol (CDP) modules, wireless access point modules, SimpleNetwork Management Protocol (SNMP) functionality, etc.) and devicedrivers (e.g., network and WLAN interface drivers) stored in persistentmemory 318 (e.g., a hard disk drive, flash memory, etc.). At start up,these software components are loaded into system memory 312 and thenaccessed and executed by processor 310.

B.4. Wireless Client

FIG. 3 illustrates for didactic purposes a hardware system 400, whichmay be used to implement a wireless client 60. In one embodiment,hardware system 400 includes a processor 402 and a cache memory 404coupled to each other as shown. Additionally, hardware system 400includes a high performance input/output (I/O) bus 406 and a standardI/O bus 408. A host bridge 410 couples processor 402 to high performanceI/O bus 406, whereas an I/O bus bridge 412 couples the two buses 406 and408 to each other. A wireless network interface 424, a system memory414, and a video memory 416 couple to bus 406. In turn, a display device418 couples to video memory 416. A mass storage 420, a keyboard andpointing device 422, and I/O ports 426 couple to bus 408. Collectively,these elements are intended to represent a broad category of computerhardware systems, including but not limited to general purpose computersystems based on the Pentium® processor manufactured by IntelCorporation of Santa Clara, Calif., as well as any other suitableprocessor.

The remaining elements of hardware system 400 are described below. Inparticular, wireless network interface 424 provides communicationbetween hardware system 400 and any of a wide range of wirelessnetworks, such as a WLAN (i.e., IEEE 802.11), WiMax (i.e., IEEE 802.16),Cellular (e.g., GSMA), etc. Mass storage 420 provides permanent storagefor the data and programming instructions to perform the above describedfunctions implemented in the system controller, whereas system memory414 (e.g., DRAM) is used to provide temporary storage for the data andprogramming instructions when executed by processor 402. I/O ports 426are one or more serial and/or parallel communication ports that providecommunication between additional peripheral devices, which may couple tohardware system 400.

Hardware system 400 may include a variety of system architectures; andvarious components of hardware system 400 may be rearranged. Forexample, cache 404 may be on-chip with processor 402. Alternatively,cache 404 and processor 402 may be packed together as a “processormodule,” with processor 402 being referred to as the “processor core.”Furthermore, certain implementations of the present invention may notrequire nor include all of the above components. For example, theperipheral devices shown coupled to standard I/O bus 408 may couple tohigh performance I/O bus 406. In addition, in some implementations onlya single bus may exist with the components of hardware system 400 beingcoupled to the single bus. Furthermore, hardware system 400 may includeadditional components, such as additional processors, storage devices,or memories.

In one embodiment, the operations of wireless client-side functionalityare implemented as a series of software routines run by hardware system400. These software routines, which can be embodied in a wirelessnetwork interface driver, comprise a plurality or series of instructionsto be executed by. a processor in a hardware system, such as processor402. Initially, the series of instructions are stored on a storagedevice, such as mass storage 420. However, the series of instructionscan be stored on any. suitable storage medium, such as a diskette,CD-ROM, ROM, etc. Furthermore, the series of instructions need not bestored locally, and could be received from a remote storage device, suchas a server on a network, via network/communication interface 424. Theinstructions are copied from the storage device, such as mass storage420, into memory 414 and then accessed and executed by processor 402. Inalternate embodiments, the present invention is implemented in hardwareor firmware.

While FIG. 3 illustrates, for didactic purposes, the hardwarearchitecture of a wireless-client according to one implementation of thepresent invention, the wireless client, however, may be implemented on awide variety of computer system architectures, such as dual-modecellular phones (e.g., cellular plus 802.11 capable devices), wirelessVoIP phones, Personal Digital Assistants (e.g., converged devices whichsupport WLAN data+voice and cellular), Laptop computers, and the like.An operating system manages and controls the operation of hardwaresystem 400, including the input and output of data to and from softwareapplications (not shown). The operating system provides an interface,such as a graphical user interface (GUI), between the user and thesoftware applications being executed on the system. According to oneembodiment of the present invention, the operating system is theWindows® 95/98/NT/XP operating system and/or Windows® CE (WinCE)operating system, available from Microsoft Corporation of Redmond, Wash.However, the present invention may be used with other operating systems,such as the Apple Macintosh Operating System, available from AppleComputer Inc. of Cupertino, Calif., UNIX operating systems, LINUXoperating systems, Symbian operating systems, and the like.

C. Location Services

As described above, the wireless network infrastructure provideslocation information via location services to wireless clients. Thelocation server 20, in one implementation, supports a plurality oflocation services, such as on-demand location services and updatelocation services, where update location services may include automaticlocation updates, conditional location updates, and the like. Anon-demand location service, for example, may provide locationinformation that describes where a particular wireless client is locatedin a particular region (e.g., within one square meter in accuracy)within in a particular city, campus, or building. An update (i.e.,subscription) location service may also provide location information(e.g., where a particular wireless client is located in a particularcity, campus, or building), but the delivery of the location informationmay be based on one or more triggers, which may include the occurrenceof one or more events including time interval triggers, movement,containment, etc. For example, the update location service may providethe wireless client with a location update periodically (e.g., every 60minutes). In one implementation, the update location service may providethe wireless client with a location update based on particularconditions. For example, in one implementation, a condition may be achange in location (e.g., when the wireless client enters or leaves aparticular area). Also, parameters may define the conditions. Forexample, in one implementation, the particular area may be defined as aparticular room, floor, building, etc. The sections below describelocation service classes and location service options in more detail.

C.1. Location Service Classes

As discussed above, location server 20 supports a plurality of locationservice classes, each corresponding to a type of location service.Location service classes may include on-demand location services and/orsubscription-based services. A location service class is a mode by whichthe wireless client receives a location service. For example, in oneimplementation, a wireless client may access a location service bytransmitting an on-demand request or by subscribing to a location updateservice. In one implementation, an on-demand request is a one timerequest for the estimated location of the wireless client. For example,after transmitting a first on-demand request, the wireless client mayneed to transmit additional on-demand requests for each desired locationupdate. In one implementation, an update service will provide locationupdates periodically or upon the occurrence of certain events. In oneimplementation, the location server 20 provides options for bothon-demand location services and update location services. The locationservices supported by location server 20, in one implementation, areindependent of each other. Accordingly, a wireless client maysimultaneously request, or subscribe to, more than one location servicesupported by location server 20.

C.2. Location Service Options

In some implementations, for one or more of the location service classes(e.g., on-demand location services or update location services),location server 20 provides to the wireless client a set of locationservice options. For example, in one implementation, for update locationservices, location service options may include receiving updates basedon one or more triggers, which may include the occurrence of one or moreevents including time interval triggers, movement, containment, etc. Forexample, in one implementation, an update may be triggered based on asignal automatically triggered by a clock according to variousschedules, periodically (e.g., every minute, every hour, etc.) or atparticular times (e.g., 12:00 p.m., 2:50 p.m., etc.). In oneimplementation, updates may be conditioned upon a threshold distancetraveled (e.g., every 5 meters), movement from a reference point,crossing a threshold region, movement in or out of an area, floor, orbuilding, etc., and the like. Update choices may include locationupdates based on other network parameters such as traffic generated bywireless clients, transmission control protocol (TCP) connections eitherfrom or to the client (i.e., as the wireless client accesses a web sitewith a specific URL, give an update of location), etc.

For both on-demand and update location services, the location server 20provides various options such as format (e.g., geospatial, CIVIC, and/orproprietary formats), resolution (e.g., location accuracy), and messageencoding options (e.g., binary vs. text-based encoding), and the like.For example, in one implementation, a format option may enable aselection of formats that the wireless network infrastructure supportsas either part of an on-demand request or an update location servicerequest. For example, in one implementation, format options may includea geospatial format (i.e., geographic coordinates), a civic format(i.e., postal or legal addresses), an LCI format, or a proprietaryformat. In one implementation, a resolution option defines the accuracyto which the wireless network infrastructure attempts to calculate alocation. For example, the resolution option may include a buildingresolution where the wireless infrastructure may resolve a location to aparticular building within a campus (or a room within a building) that awireless client resides. Further, the resolution option may include awireless access point resolution, where the wireless networkinfrastructure may resolve a location to a particular wireless accesspoint to which a wireless client is connected. Further, the resolutionoption may include an XY resolution, where the wireless networkinfrastructure may resolve a location to a specific XYZ point within thecoordinate space. In one implementation, the datum used for XYResolution is relative to the location format chosen. In oneimplementation, an encoding option may include text (e.g., extensiblemarkup language (XML)) or binary options (e.g., binary representation ofXML). In one implementation, a security option may include a requirementthat location information be digitally signed for secure distribution.

In one implementation, location server 20 may give a high priority toemergency requests. For example, an e911 location server 20 may providelocation information to a wireless client so that the wireless clientcan include the location information as part of emergency callsignaling.

D. Overview of Message Flows for Location Services

D.1. On-Demand Location Services

FIG. 4 is a diagram illustrating a possible message flow among awireless client 60, a central controller 43, and a location server 20 inaccordance with one implementation of the present invention. FIG. 4illustrates one implementation where central controller 43 transmits alocation services advertisement, which indicates location services thatlocation server 20 supports. Central controller 43 also transmits pathloss measurement (PLM) parameter request (PLM request). As described inmore detail below, PLM parameters are parameters according to which awireless client transmits wireless frames that are detected by one ormore access points (or other wireless receivers associated with thewireless network infrastructure). Upon receiving the location servicesadvertisement and PLM request, wireless client 60 transmits a locationservice request (i.e., an on-demand location service request) and a PLMresponse, which includes measurements results, to central controller 43,which forwards the location service request and measurement results tolocation server 20. Location server 20 then transmits a location serviceresponse to central controller 43, which then forwards the locationservice response to wireless client 60. The location servicesadvertisement, PLM request and response, location service request andresponse are described in more detail below.

D.2. Update Location Services

FIG. 5 is a diagram illustrating a possible message flow among awireless client 60, a central controller 43, and a location server 20 inaccordance with one implementation of the present invention. FIG. 5illustrates one implementation where central controller 43 transmits alocation services advertisement to wireless client 60. Upon receivingthe location services advertisement, wireless client 60 transmits alocation service request (i.e., an update location service request) tocentral controller 43, which forwards the location service request tolocation server 20. In one implementation, location server 20 transmitsa subscribe acknowledgement and a PLM request to central controller 43,which forwards the subscribe acknowledgement and PLM request to wirelessclient 60. Wireless client 60 then transmits a PLM response to centralcontroller 43, which transmits measurements results to location server20. Location server 20 transmits a location service response to centralcontroller 43, which forwards the location service response to wirelessclient 60. In one implementation, wireless client 60 may transmit alocation unsubscribe request to central controller 43, which thenforwards the unsubscribe request to location server 20. The unsubscriberequest terminates the update location service subscription. Locationserver 20 then transmits an unsubscribe acknowledgement to centralcontroller 43, which forwards the unsubscribe acknowledgement towireless client 60.

E. Location Services Advertisement, Presentation, and Requests

The following sections describe how a wireless network infrastructureadvertises one or more location services to a wireless client and howthe wireless client requests or subscribes to one or more locationservices.

E.1. Advertisement of Location Services

As described above, in one implementation, location server 20 provides alist of its available supported location services to wireless clients 60via the wireless network infrastructure. More specifically, locationserver 20 provides to central controller 70 a list of available locationservices, and central controller 70 advertises the available locationservices to wireless clients 60 via wireless access points 50. In oneimplementation, during a presentation phase, the wireless clientreceives the advertisements and then presents the available locationservices to one or more applications of the wireless client. Thewireless network infrastructure advertises the one or more locationservices supported by location server 20 in a variety of manners. Forexample, in one implementation, the wireless network infrastructure mayadvertise the location service types and attributes in a locationservice Information Element (location service IE) appended to wirelessnetwork management frames, such as Beacon Frames, Probe Response Frames,Authentication Response Frames, and Association Response Frames. Alocation service IE is an element that indicates what location servicesare available and, in some implementations, the attributes of theavailable location services. The location service IE is described inmore detail below in connection with FIGS. 6 and 7. In oneimplementation, the information IE may be advertised in other frametypes, such as a management frame specifically dedicated to locationservice advertisements.

E.2. Presentation of Location Services

FIG. 6 is a flow chart illustrating a process flow, according to oneimplementation of the present invention, implemented at the wirelessclient 60. In a presentation phase, a wireless network interface driverof the wireless client 60 (e.g., an 802.11 MAC driver) determines if ithas received a management frame (502). In one implementation, wirelessclient 60 may receive management frames during various processes, suchas while scanning the RF environment for access points, and/or during anassociation or authentication process. If wireless client 60 receivessuch a management frame, wireless client 60 then determines if themanagement frame includes a location service IE, if any (504).

FIG. 7 is a data structure of an exemplary location service IE accordingto one implementation. In one implementation, the location service IEincludes an element identification (element ID) field, a length field,an organization unique identifier. (OUI) field, a service field, and anoption field. In one implementation, the element ID identifies thewireless client and the TSID identifies an emergency message. In oneimplementation, the TSID field may contain the same value as that in thecorresponding TSPEC request (or TCLAS element if present). As describedin more detail below, in one implementation, the bandwidth use fieldcontains a value that may identify a type or “use” of call (e.g.,whether the call is emergency-related). In one implementation, thelocation service IE includes various information such as an element IDfield, a services field, and an option field. In one implementation, theelement ID field describes an IEEE 802.11 assigned value forvendor-specific information elements. In one implementation, theservices field describes the location service classes that the wirelessnetwork infrastructure supports. In one implementation, the option fielddescribes location service attributes and options corresponding to thelocation service classes that the wireless network infrastructuresupports.

In one implementation, the position of each bit in the services fieldcorresponds to a location service class (e.g., on-demand locationservice or update location service), and the value of each bit indicateswhether location services in the particular location service class isavailable (e.g., 0=available; 1=not available). Similarly, in oneimplementation, the position of each bit in the option field correspondsto a location service option (e.g., geospatial, CIVIC, proprietaryformat, building resolution, wireless access point resolution, x-ycoordinate resolution, binary encoding text-based encoding, etc.), andthe value of each bit indicates whether the particular location optionis available (e.g., 0=available; 1=not available). In oneimplementation, if a bit is unused, the bit may be reserved foradditional classes, options, etc.

If the management frame includes a location service IE, the wirelessnetwork interface driver processes the location service IE (506). In oneimplementation, the wireless network interface driver parses theinformation in the location service IE and populates a data structure,such as a location services table, with information from the locationservice IE. In one implementation, the wireless network interface driverupdates the location service data structure as subsequent locationservices advertisements are received. One or more applications installedon the wireless client may then access the location service datastructure to determine available location services and attributes. Inone implementation, the wireless network interface driver furthersupports application programming interfaces (APIs) that allow the one ormore applications to make calls to the driver to request that a locationservice request frame be transmitted. The calls can include parameters,such as the selected location service and one or more optionscorresponding to the selected location service. For example, in asubscription phase, an application may select one or more of thelocation services, such as a location update service, and invoke thewireless network interface driver to transmit a location service requestidentifying the location update service.

E.3. Request for Location Services

FIG. 8 is a flow chart illustrating a process flow, according to oneimplementation of the present invention, implemented by the wirelessnetwork infrastructure (in one implementation, at the central controller70). In one implementation, during a request phase, the driver of thewireless client 60 transmits a location service request to the centralcontroller 70, which the wireless network infrastructure forwards to thelocation server 20. Central controller 70 monitors and receives alocation service request from wireless client 60 (602). In oneimplementation, the location service request may identify one or morelocation services. In one implementation, central controller 70 mayvalidate wireless client 60. For example, central controller 70 maydetermine whether wireless client 60 is blacklisted. In oneimplementation, for denied subscriptions, the infrastructure willprovide an error/fault code in response to the wireless client. Centralcontroller 70 then determines if the location service request is anon-demand request (604). If the location service request is an on demandrequest, central controller 70, in one implementation, gathers locationdata, such as signal strength information, to be used to compute theestimated location of the wireless client (606). In one implementation,central controller 70 requests location data from the wireless client.For example, the location data may include the signal strength observedby the wireless client of transmissions by one or more access points 50of the wireless network infrastructure. In another implementation, thelocation data may include signal information obtained by one or moreaccess points 50 of the wireless network infrastructure. In someimplementations, the central controller 70 (or some other element of thewireless network infrastructure) may direct the wireless client totransmit a series of frames on one or more selected operating channelsto allow one or more access points 50 of the wireless networkinfrastructure to detect the signal of the wireless client. In oneimplementation, the location data may include measurement informationsuch as received signal strength information or other locationmeasurement information (e.g., Time of Arrival (TOA) or Time Differenceof Arrival (TDOA) information). Central controller 70 then forwards thelocation service request and collected location data to the locationserver (608).

If the location service request is not an on-demand request (604),central controller 70 forwards the location service request to locationserver 20 (610). Central controller 70 then generates path lossmeasurement (PLM) parameters (612). The PLM parameters are parametersaccording to which the wireless client transmits wireless frames thatare detected by one or more access points 50 (or other wirelessreceivers associated with the wireless network infrastructure). Asabove, one or more detected attributes of the RF signals correspondingto the frames are forwarded to location server 20. In oneimplementation, the central controller 70 transmits the PLM parametersto the wireless client (612). In one implementation, the transmission ofthe PLM parameters may correspond to one or more attributes of awireless frame transmission schedule where the wireless client transmitsa plurality of wireless frames. In one implementation, the wirelessframe transmission schedule may include one or more of the following PLMparameters: 1) an interval between bursts of wireless frames, 2) thenumber of wireless frames in a burst, 3) the RF channels on which totransmit the wireless frames, and 4) an overall duration (expressed, forexample, as a total number of bursts or as a period of time). In oneimplementation, the PLM parameters may specify that the wireless clientgather and transmit wireless frames to particular wireless access pointsoperating on respective RF channels (e.g., channels 1, 6, and 11) atparticular time periods (e.g., every minute). After central controller70 collects the location data, it then forwards the location data tolocation server 20. Location server 20 may then provide locationservices to wireless client 60. The location data enables locationserver 20 to provide location updates as often as the location data isupdated.

In one implementation, the PLM parameters may vary depending on thelocation services and/or attributes selected by the wireless client. Forexample, a first update location service may require shorter intervalsbetween bursts, while a second update location service may require agreater number of wireless frames in each burst. Accordingly, centralcontroller 70, in one implementation, is configured to parse thelocation service request and identify one or more suitable PLMparameters to provide to the wireless client based on the one or moreselected location services and/or options.

In one implementation, for security and privacy reasons, centralcontroller 70 may provide a given wireless client only the locationinformation of that wireless client. In another implementation, a givenwireless client may request location information for other entities inthe network and may receive such location information if authorized.

FIG. 9 is a flow chart illustrating a process flow, according to oneimplementation of the present invention, implemented at a locationserver. As shown in FIG. 9, location server 20 receives the locationservice request (702) and determines whether the location servicerequest is an on-demand request (704). If the not, location server 20adds the wireless client to the location service(s) identified in thelocation service request (706). If the location service request is anon-demand request, location server 20 computes the estimated locationbased on received location data (i.e., measurement results from a PLMresponse) (708). Location server 20 then returns the computed locationto the wireless client.

The present invention has been explained with reference to specificembodiments. For example, while embodiments of the present inventionhave been described as operating in connection with IEEE 802.11networks, the present invention can be used in connection with anysuitable wireless network environment. Other embodiments will be evidentto those of ordinary skill in the art. It is therefore not intended thatthe present invention be limited, except as indicated by the appendedclaims.

1. Logic for requesting one or more location services provided by anetwork infrastructure, the logic encoded in one or more media forexecution and when executed operable to: access one or more wirelessadvertisements that identify one or more location services; andtransmit, responsive to selection of one or more of the identifiedlocation services, a location service request identifying one or more ofthe selected location services.
 2. The logic of claim 1 wherein thelogic is operable to present to an application program data allowing forselection of one or more location services identified in wirelessadvertisements.
 3. The logic of claim 1 wherein at least one locationservice comprises an on-demand location service.
 4. The logic of claim 1wherein at least one location service comprises an update locationservice.
 5. The logic of claim 1 wherein the one or more wirelessadvertisements further comprise one or more location service optionscomprising one or more of a format option, resolution option, and anencoding option.
 6. The logic of claim 1 wherein the one or morewireless advertisements are wireless management frames, and wherein theone or more location services are contained in information elementsappended to the wireless management frames.
 7. In a wireless client, amethod comprising: accessing one or more wireless advertisements thatidentify one or more location services; and transmitting, responsive toselection of one or more of the identified location services, a locationservice request identifying one or more of the selected locationservices.
 8. The method of claim 7 further comprising presenting to anapplication program data allowing for selection of one or more locationservices identified in wireless advertisements.
 9. The method of claim 8wherein at least one location service comprises an on-demand locationservice.
 10. The method of claim 8 wherein at least one location servicecomprises an update location service.
 11. The method of claim 7 whereinthe one or more wireless advertisements further comprise one or morelocation service options comprising one or more of a format option,resolution option, and an encoding option.
 12. The method of claim 7wherein the one or more wireless advertisements are wireless managementframes, and wherein the one or more location services are contained ininformation elements appended to the wireless management frames.
 13. Awireless client comprising: means for wirelessly communicating with awireless network; means for accessing one or more wirelessadvertisements that identify one or more location services; and meansfor transmitting, responsive to selection of one or more of theidentified location services, a location service request identifying oneor more of selected location services.
 14. Logic for providing one ormore location services provided by a network infrastructure, the logicencoded in one or more media for execution and when executed operableto: transmit wireless frames advertising one or more location services;and forward location service requests received from wireless clients toa location server.
 15. The logic of claim 14 wherein the logic isoperable to collect location data for a wireless client if a receivedlocation service request is an on-demand request.
 16. The logic of claim14 wherein the logic is operable to generate path loss measurementparameters (PLM) including a radio transmission schedule including oneor more of an interval between bursts, a number of bursts, and one ormore radio channels on which to transmit.
 17. In a wireless networkinfrastructure node, a method comprising: transmitting wireless framesadvertising one or more location services; and forwarding locationservice requests received from wireless clients to a location server.18. The method of claim 14 further comprising: collecting location datafor a wireless client if a received location service request is anon-demand request.
 19. The method of claim 14 further comprising:generating path loss measurement parameters (PLM) including a radiotransmission schedule including one or more of an interval betweenbursts, a number of bursts, and one or more radio channels on which totransmit.
 20. An apparatus comprising: means for transmitting wirelessframes advertising one or more location services; and means forforwarding location service requests received from wireless clients to alocation server.
 21. A location server comprising: one or moreprocessors; a memory; a network interface; and a management application,physically stored in the memory, comprising instructions operable tocause the one or more processors and the wireless network server to:provide a list of available location services to one or more elements ofa wireless network; receive one or more location service requests fromthe one or more wireless clients; and provide one or more locationservices to the one or more wireless clients based on the locationservice requests.
 22. In a location server, a method comprising:providing a list of available location services to one or more elementsof a wireless network; receiving one or more location service requestsfrom the one or more wireless clients; and providing one or morelocation services to the one or more wireless clients based on thelocation service requests.